Spreading key/value pairs across multiple memcached servers

[Chris Hartjes]

/me bows deeply at the feet of the master

Brad, thanks for clearing that up.  The boss' concern now is (and I
quote) "does it always talk to the same server when trying to find out
where a key is".  If we have three memcached servers, I am hoping that
it doesn't always talk to the first one when it asks "by the way, can
you tell me what server this key is on?"


On Wed, 1 Dec 2004 08:41:34 -0800 (PST), Brad Fitzpatrick
<brad at danga.com> wrote:
> Fortunately (for you having to do work) you boss and you misunderstand how
> memcached works.  :)
> 
> Memcached is a two-layer hash.  The client (your app, or rather the
> library you're using) does the first layer hash --- based on the key it
> calculates which server to use.  Then, your app (via the library) contacts
> that server and the server has a hash within it.
> 
> There is so search order (because it never searches) and there is no
> master or primary memcached server.
> 
> You just add as many as you want and the load balancing is automatic and
> even.
> 
> - Brad
> 
> 
> 
> 
> On Wed, 1 Dec 2004, Chris Hartjes wrote:
> 
> > I had a chat about this with my boss, and his concern is not that we
> > distribute the keys evenly, his concern is distributing the request to
> > find out what server a key is sitting on.  I figure he doesn't want
> > the first memcached server getting constantly pounded with requests
> > for the location of a key, while the second server could be helping
> > out in that regards.
> >
> >
> > On Wed, 01 Dec 2004 11:21:59 -0500, Greg Whalin <gwhalin at meetup.com> wrote:
> > > A good hashing algorithm should take care of this for you.  I am under
> > > the impression that the currently used default for the perl and php
> > > clients is using a new alg based on a crc32 checksum that gets very even
> > > key distribution, so I don't see this as being an issue.
> > >
> > >
> > >
> > > Chris Hartjes wrote:
> > > > My boss has requested that if we are to implement the use of memcached
> > > > for our site, that we need to "load balance" the data we place in
> > > > multiple memcached servers.  I guess the concern is that we would be
> > > > overtaxing one memcached server while other memcached servers are
> > > > being underutilized.
> > > >
> > > > Thoughts?  Comments?
> > > >
> > >
> >
> >
> > --
> > Chris Hartjes
> >
> > "I know monkeys, and monkeys are good people!"
> >
> >
> 


-- 
Chris Hartjes

"I know monkeys, and monkeys are good people!"